East Lyme — After what First Selectman Mark Nickerson said has been a proposal 20 years in the making, developers building a proposed Costco big-box store have finally broken ground.

The store, at Gateway Commons, will be located near Interstate 95’s Exit 74 and will serve as the initial phase of the retail component proposed for the Gateway Commons development — a 200-acre site between Exits 73 and 74.

Gateway developers have already built 280 apartments near Exit 73 as part of that development and recently proposed an additional 120 rental units to be built out over upcoming years.

“We are happy to welcome Costco to town,” Nickerson said Sunday. “This project has been on the table for 20 years and the town has been patient.”

“This is the last large undeveloped commercially zoned property in our town, and we are happy to see it developed for economic gain,” he said, explaining that when both Costco and the proposed apartments are completed, the town expects an additional $800,000 to $1 million in annual tax revenue.

The proposed 158,684-square-foot Costco store, which would include an on-site gas station, was approved by both the zoning and inland wetland commissions earlier this year and received both its building and zoning permits in December.

Though earlier projections had detailed a September groundbreaking for the Costco building, a lengthier-than-expected permitting process delayed the project.

It is unclear now whether plans to construct the Costco store will still take place over 90 days next summer, as was stated in a previous timeline.

Newton Brainard, vice president of development and acquisition for The Simon Konover Co. of West Hartford, which is developing the Gateway site with KGI Properties of Providence, said Sunday that "in general, we anticipate a 2020 opening."

He said the schedule for an opening date “will remain fluid” as Costco developers work with contractors, the Department of Transportation and the town, as well as local electric, gas, telephone and cable companies, to complete construction. An official opening date should be set by spring, he said.

Plans for building a temporary roadway infrastructure by Exit 74 to ease incoming traffic in and out of Costco are also underway and are expected to begin by spring, he said.

That road, which will extend the I-95 southbound on- and off-ramps at Exit 74 to a frontage road running by Pools Etc., will allow drivers coming off the interstate to either turn left toward Costco or right toward Route 161 after hitting a stop light.

Brainard has said he is not expecting a major disruption in traffic flow during and after construction. He said the plan is to build the interior road leading up to Costco over a day or two and then extend the on- and off-ramps to that road.

The state approved a permit for those changes in August, and they will be the first of many as the state also seeks to permanently fix and redesign the Exit 74 interchange.

Construction for those larger adjustments is still two to three years away, Nickerson said.

DOT will be speaking with town officials in April about those changes.

“The economic development that is being brought by Costco to the town and the state makes this restructuring a priority for the state,” Nickerson said. “It is exciting and it is going to be a big deal and a big draw.”

m.biekert@theday.com